Two-stage material cooler

ABSTRACT

A two-stage material cooler particularly adapted for cooling burning or burned material. The cooler includes a first stage direct cooler such as a grate cooler wherein air is blown through the material as it is discharged from a furnace such as a rotary kiln. The air heated by the hot material is returned as combustion air to the furnace. The partially cooled material is passed through a material breaker and supplied to an indirect cooler for further cooling. The indirect cooler includes a plurality of bins each having a plurality of spaced apart tubes therein. Cooling fluid such as air or water is passed through these tubes. The material to be cooled is placed in the top of these bins and passes downwardly therethrough to be discharged from the bottom of the bins. As material passes through the bins, it contacts the cooling tubes and is thereby cooled.

United States Patent Kayatz 154] TWO-STAGE MATERIAL COOLER [72] Karl-Heinz Kayatz, Hamburg-Nichstedten, Germany Claudius Peters, Aktiengesellschatt Feb. 23, 1971 Inventor:

Assignee: Filedz Appl. No.:

[30] Foreign Application Priority Data References Cited I UNITED STATES PATENTS Treschow ..165/90 X Karlsson ..34/57 A Schleicher ..34/57 A Newhouse ..263/32 R [451 Dec. 12,1972.

FOREIGN PATENTS OR APPLICATIONS 635,998 9/1936 Germany ..34/135 Primary Examiner-Frederick L. Matteson Assistant Examiner-Theophil W. Streule Attorney-Jack L. Prather and Frank H. Thomson [5 7] ABSTRACT A two-stage material cooler particularly adapted for cooling burning or burned material. The cooler includes a first stage direct cooler such as a grate cooler whereinair is blown through the material as it is discharged from a furnace such as a rotary kiln. The air heated by the hot material is returned as combustion air to the furnace. The partially cooled material is passed through a material breaker and supplied to an indirect cooler for further cooling. The indirect cooler includes a plurality of bins each having a plurality of spaced apart tubes therein. Cooling fluid such as air or water is passed through these tubes. The material to be cooled is placed in the top of these bins and passes downwardly therethrough to be discharged from the bottom of the bins. As material passes through the bins, it contacts the: cooling tubes and is thereby cooled.

12 Claims, 4 Drawing Figures PATENTED 12 I973 3. 705,620

sum 1 0F 2 INVENTOR ATTORNEY KARL-HEl/VZ m )2: T2

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A INVENTOR KARL -H//VZ K4 YATZ ATTORNEY l TWO-STAGE MATERIAL COOLER BACKGROUND OF THE INVENTION This invention relates to a two-stage cooler for cooling coarse grained burning material and in particular to a two-stage cooler for cooling hot cement clinker which is discharged from a rotary kiln.

Grate coolers such as that shownin US. Pat. No. 2,137,158 and subsequently issued US. patents are in common usage in the cooling of hot material. Such material coolers receive hot material from a furnace. As the material is advanced through the cooler, air is blown up through the material. The air which is blown through the hot material is heated and a portion of it is returned to the furnace as combustion air.

The principal advantage of such grate coolers isthat they permit recuperation of a portion of the heat from the hot material being cooled. However, only a portion of the large volume of air blown through the hot material can be used by the furnace. The remaining air must be exhausted from the system.

As air passes through the hot material, it entrains dust and particulate matter which must be removed from the air before it is exhausted to atmosphere. This is the principal disadvantage of grate coolers. The large volume of air which is required to cool the material necessitates the use of large, expensive filtering equipment such as a baghouse, electrostatic precipitator or other high efficiency air filter.

It is true that grate coolers are known in which the cooling air is passed through the cooling bed and is directed to the kiln as combustion air; however, because of simplicity, the preferred designs are those which pass air through a single hot grate section whereas the remaining cooling air, which is about twothirds of the total cooling air, is led to atmosphere after heating by some 100 C. Whereas, for instance for the cooling of cement clinker approximately two-thirds of the total temperature reduction, namely the cooling from l,350 to about 500 C. are achieved with only one-third of the total air and with little effort, the last third of the total temperature reduction from about 500 C. to below 100 C. necessitates two-thirds of the air, and considerable expenditure of machines and energy is required to dedust this portion of the air.

Although other types of coolers are known, they do not have the desirable advantage of permitting heat recuperation. Such other coolers include rotary coolers and satellite coolers. These coolers have the advantages of not requiring extensive air filtering apparatus.

SUMMARY It is, therefore, the principal object of this invention to provide a cooler for hot material which has the advantages of grate coolers as well as the advantages of other types of coolers.

It is another object of this invention which has the heat recuperative advantages of grate coolers while avoiding the disadvantage of grate coolers of requiring the use of extensive high efficiency air filtering apparatus.

It is a further object of this invention to provide a hot material cooling apparatus which includes an initial direct cooler stage which permits heat recuperation and a second stage indirect cooler which eliminates the necessity of using dust collecting apparatus.

In general, the foregoing and other objects will be carried out by providing a two-stage cooler for hot material discharged from a furnace comprising a first cooling apparatus including means for receiving hot material from the furnace, means for moving the material through the first cooling apparatus, means for passing cooling air through the hot material, and means for conducting the cooling air heated by the hot material to the furnace; a second cooling apparatus including at least one conduit means for receiving material to be cooled and discharging cooled material, a plurality of spaced apart tubes mounted in said conduit means transverse to the flow path of material through said conduit means, and means for supplying cooling fluid to said tubes whereby material to be cooled comes into heat exchange relation with said cooling tubes and is thereby cooled; and means for conducting material from said first cooling apparatus to said second apparatus.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described in connection with the annexed drawing wherein:

FIG. 1 is a diagrammatic view of the two-stage cooling apparatus of the present invention;

FIG. 2 is a sectional view of a portion of the present invention;

FIG. 3,is a sectional view of one portion of the second cooling stage of the present invention; and

FIG. 4 is a diagrammatic view of a modification of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is passed on the task to create a cooler requiring less expenditure for the second cooling stage.

The solution as per this invention consists in that, that the second stage is a cooler operating indirectly, which consists of a hopper or shaft with a multitude of cooling surfaces arranged across the shaft. A cooling fluid such as air or water ispassed through the cooling surfaces. Hot material such as clinker broken to a certain maximum size passes by means of gravity through the shafts or hoppers. Level controllers regulate the flow through the hoppers. The second stage indirect cooler enables the first cooling stage to be only as large as is necessary for the preheating of the combustion air for the kiln.

Prior to the present invention, it was believed that the direct cooling of cement clinker was the simplest and most economical method of cooling, because not only is a good heat transfer possible between the clinker grain'and the passing cooling media but also can simple and rugged cooler designs be chosen. The invention surprisingly shows, that the indirect cooling in the second cooling stage is effective and more economical since the cooling media does not have to be dedusted.

It is true, that indirect coolers for the cooling of burning material are known, but only for fine and granular material, which by aeration can be passed by cooling surfaces or which at least can be fluidized whereby it can be conditioned in heat exchangers, which essentially are designed around the known prin ciple of heat exchangers for liquid or gaseous media. These heat exchangers were thought not to be applicable to the coarse clinker material because they lacked the ability to intensify the heat transfer between the material to be cooled and the cooling surfaces by fluidization. Indeed, the known indirect coolers for the cooling of fine material are not usable for cement clinker because in the hot stage it cannot economically be brought to the degree of fineness, which would be necessary for the pneumatic fluidization. The present invention is based on the surprising conclusion, that despite this opinion a certain heat exchanger design is very well suited for unbroken clinker and in fact allows a particularly economical method of operation. This design is of the method of construction mentioned above, in which the broken clinker moves by gravity along cooling surfaces, preferably staggered. This movement however, is completely different from that known in heat exchangersfor fine or at least fluidizable material. The velocity, namely, of the clinker particles in relation to the cooling surfaces is extremely low, so that during the relatively long retention time of every clinker particle on a cooling surface a sufficient cooling is ensured. Advantageously, the distances between the cooling surfaces are of a magnitude, which is not considerably above that of the largest clinker particle, so that each clinker particle contacts or nearly approaches the cooling surfaces. To be more specific the distance of the cooling surfaces has to be approximately twice to eight times as much as the diameter of the biggest clinker particle, so that on the one hand there is favorable heat exchanging and on the other hand the danger of plugging is avoided. The cooler parts carrying the cooling surfaces are arranged appropriately in multitude staggered along the way of the clinker through the cooler, so that those particles, which have lain approximately in the middle between two cooling surfaces have the opportunity to touch a cooling surface.

In accordance with the present invention the second cooling stage can be formed by a multitude of cooling shafts arranged in series so that the cooling elements can be easily individually mounted and if necessary repaired. The arrangement in series is not only recommended so that the cooling surfaces arranged crosswise can be taken out or mounted sideways, but also because the particularly advantageous charging method of the present invention may be used.

The charging equipment includes a conveyor arranged horizontally above the shaft or shafts, which takes the material at a point and transports it in a direction opposite from where, and only if, it exceeds a predetermined filling stage of the shaft or shafts. In'

other words this means, that the material charged at one end will only then be carried on by the conveyor, when the filling level reaches the conveyor. This charging method has the advantage, that along its total length the shaft or all the shafts will be completely filled except for a small last section of the shaft or except for the last shaft within a group.

The controlling of the filling grade is appropriately being done in this way, that the filling grade indicator is located in this last section and that this indicator controls the discharge of the cooler. Upon reaching a certain lower level the rate of discharge is being slowed down, whereas it is being increased upon exceeding a certain level. The level controller in this described ex ample is a simple filling grade indicator. It is understood, that any other device can be used instead, which only is suited to detect the level in the shaft or shafts. Also an indication for instance is the power used by the conveyor. Having too low a filling grade in the shaft or shafts the level reaches the conveyor only in a small part, so that the power used accordingly is low, whereas it is high in the reversed case.

The cooling surfaces arranged crosswise in the cooling shaft are formed per the invention by channels having a nearly rhombic cross section and with the longer diameter arranged vertically. This cross section has the advantage, that on the one hand the friction of the material is minimal and on the other hand the resistance against the forces exerted by the friction of the material is a maximum. Further, this cross section has the particular advantage, that the channels in respect to each other can be arranged in such a way that the flow path for the material to be cooled formed in between them has an approximately constant cross section. This can exactly be achieved for a rhombic shape. However, cross sections of an approximately rhombic shape also have this advantage sufiiciently, for instance per the invention one particularly advantageous cross section in I which a pair of lateral rhombic surfaces are substituted by a curved surface.

Referring to the drawing and in particular to FIG. 1, there is shown a furnace such as a rotary kiln 1 which supplies hot material to be cooled to a first stage cooling apparatus 2. The first stage cooling apparatus may be a grate cooler such as shown in US. Pat. No. 2,137,158. The grate cooler includes a plurality of alternately reciprocating and stationary grates 3 for moving the material from the inlet of the cooler 2 to the outlet of the cooler. A fan means 4 supplies cooling air to a plenum chamber 5 below the grates 3 and the cooling air is blown through the hot material 6. The air which passes through the material 6 is heated by such material and returned to the rotary kiln 1. The heat recuperation provided by grate coolers is their primary advantage over other types of material coolers. Combustion air supplied to the kiln 1 is already at a high temperature thereby making the kiln more efficient.

A material breaker 8 is positioned at the discharge end of the cooler 2. After passing through the breaker 8, the material drops through discharge 7 onto a belt conveyor 10. The belt conveyor conveys the partially cooled material to a bucket elevator 11. The bucket elevator lifts the partially cooled material to a conduit 12 having a screen 14 mounted therein. Material of the desired size passes through the screen 14 into an inlet 16 of a second cooling stage 18. Oversize material is returned to the breaker 8 by means of a suitable conduit 19.

The suitably sized material is discharged from conduit 16 intoa first conduit means or hopper 20. When the hopper 20 is filled, a drag chain type conveyor 22 brings material overflowing hopper 20 into subsequent hoppers or conduit means 24, 25, and 26. The latter hopper 24 is not supplied with material to be cooled until the hopper 20 is filled and so on.

Material to be cooled passes through each of the hoppers 20, 24, 25, and 26 by means of gravity and is discharged onto a suitable conveyor 29. In FIG. 2 I have shown an arrangement for controlling the flow of mateaialthrough the hoppers 20, 24, 25, and 26. Such arrangement includes a reciprocating bar 30 operated by gears 31 which are connected to suitable drive means (not shown) and having a grate means 32 operatively connected thereto. -A plurality of openings 34 in the bottom of the bins 20, 24, 25, and 26 are periodically covered and uncovered by the reciprocation of the grate 32. By controlling the speed of reciprocation 1 of the grate 32 the amount of time the material remains in each of the hoppers can be controlled thus permitting control of the temperature of material leaving the hoppers. Level sensors 35 and 36 may be provided in the last hopper 26 for controlling the discharge from the hoppers by controlling the grate 32 or by controlling the input to the cooling apparatus from kiln l.

A plurality of cooling tubes 40 are mounted in each of the hoppers 20, 24, 25, and 26. These cooling tubes are mounted transverse to the flow of material through the conduit means 20,24, 25, and 26. Referring to FIG'.

3, cooling fluid such as air is supplied to each of the tubes 40 by means of fans 42 through conduits 44 and 45. As the cooling fluid passes through the tubes 40, heat is removed from the material in an indirect heat exchange relation. After passing through the tubes 40, the air may be exhausted to atmosphere through conduit 47 or conducted to the plenum chamber 5 either directly or through fan 4 of the first cooler. Because the air never comes in direct contact with the material to be cooled, the air does not entrain dust and particulate matter in the material to be cooled and therefore does not need to be passed through a high eificiency dust collecting apparatus prior to being exhausted to atmosphere. This enables a substantial reduction in cost of a material cooling system.

If desired, the fans 42 may be replaced by liquid pumps and a cooling liquid-such as water may be supplied to the tubes 40. In either case, as shown in FIG. 3, the tubes and fans 42 may be arranged so that more cooling fluid is supplied to the upper part of the bins than to the lower parts. The flow of cooling fluid is counter to the flow of hot material through the hoppers 20,24, 25, and 26.

As shown in FIG. 2 the cooling tubes 40 are preferably substantially rhombic in configuration and are staggered. The rhombic configuration permits the material to pass through the hoppers 20, 24, and 26 without collecting on the tubes. The staggered arrangement insures that all material passing through the hoppers comes into heat exchange relationship with the cooling tubes 40. Preferably, the tubes 40 are spaced apart a distance such that the particles of material entering the hoppers will be a certain minimum distance from the cooling tubes.

In FIG. 4 I have shown a modification wherein the screen 14 of FIG. 1 and the return duct 19 have been eliminated. In the embodiment of FIG. 4 the first cooler 2 has been provided with screen-like grates 50 near the discharge end of the cooler 2 so that materiaLwhich is of the desired size, to be supplied to the second stage cooler 18 can by-pass the breaker 8. Proper size material passes through the screens 50 and a discharge 52 onto the conveyor and then to the elevator 11. Material which is a size which necessitates breaking is then conducted to the breaker 8 and through discharge 7 to the conveyor 10. This arrangement improves the efficiency of the breaker 8.

From the foregoing, it objects of the invention have been carried out. A twostage cooling apparatus has been provided which retains the advantages of a direct cooling apparatus and eliminates the disadvantages of such direct cooling apparatus. The heat recuperating advantage of a direct cooler has been retained. The very hot material which is discharged from the furnace has air blown through it and as the air is heated, it is returned to the furnace as combustion air. Subsequent cooling is done by an indirect method thereby .eliminating the necessity of using expensive high efficiency dust collectors such as baghouses or electrostatic precipitators.

I claim:

1. A two-stage cooler for hot material discharged from a furnace comprising:

a first cooling apparatus including means for receiving hot material from the furnace, means for moving the material through the first cooling apparatus, means for passingcooling air through the hot material, and means for conducting the cooling air heated by the hot material to the furnace; second cooling apparatus. including at least one conduit means for receiving material to be cooled and discharging cooled material, a plurality of spaced apart tubes mounted in said conduit means transverse to the flow path of material through said conduit means, and means for supplying cooling fluid to said tubes whereby material to be cooled comes into heat exchange relation with said cooling tubes and is thereby cooled; and

means for conducting material from said first cooling apparatus to said second apparatus.

2. The cooler .of claim 1 wherein the conduit means of said second cooling apparatus is substantially vertical and material to be cooled is supplied to the top of said conduit means and discharged from the bottom thereof, and material flows through said conduit means by gravity.

3. The cooler of claim 2 wherein said second cooling apparatus further includes means for controlling the length of time material is retained in said conduit means.

4. The cooler of claim 1 further comprising breaker means positioned at the discharge end of said first cooling apparatus for reducing the size of material supplied to said second cooling apparatus.

5. The cooler of claim 4 further comprising screen means mounted in said means for conducting material from said first cooling apparatus to said second cooling apparatus for controlling the maximum size of material supplied to the second cooling stage, and means for returning oversize material to said breaker means.

6. The cooler of claim 5 wherein said means for conducting material from said first cooling apparatus to said second cooling apparatus includes an elevator.

7. The cooler of claim 4 wherein said first cooling apparatus includes screen means positioned before said breaker means and bypass means for conducting small size material around said breaker means to said means for conducting material to said second cooling apparatus.

8. The cooler of claim 1 wherein the tubes of said second cooling apparatus are substantially rhombic in cross section.

should be apparent that the V 9. The cooler of claim 8 wherein the tubes of said second cooling apparatus are staggered in said conduit means.

10. The cooler of claim 9 wherein the means for supplying cooling fluid to the tubes of the second cooling apparatus includes at least one fan for forcing gaseous fluid through said tubes.

11. The cooler of claim 9 wherein the means for supplying cooling fluid to the tubes of the second cooling apparatus includes means for supplying liquid to the tubes. 

1. A two-stage cooler for hot material discharged from a furnace comprising: a first cooling apparatus including means for receiving hot material from the furnace, means for moving the material through the first cooling apparatus, means for passing cooling air through the hot material, and means for conducting the cooling air heated by the hot material to the furnace; a second cooling apparatus including at least one conduit means for receiving material to be cooled and discharging cooled material, a plurality of spaced apart tubes mounted in said conduit means transverse to the flow path of material through said conduit means, and means for supplying cooling fluid to said tubes whereby material to be cooled comes into heat exchange relation with said cooling tubes and is thereby cooled; and means for conducting material from said first cooling apparatus to said second apparatus.
 2. The cooler of claim 1 wherein the conduit meanS of said second cooling apparatus is substantially vertical and material to be cooled is supplied to the top of said conduit means and discharged from the bottom thereof, and material flows through said conduit means by gravity.
 3. The cooler of claim 2 wherein said second cooling apparatus further includes means for controlling the length of time material is retained in said conduit means.
 4. The cooler of claim 1 further comprising breaker means positioned at the discharge end of said first cooling apparatus for reducing the size of material supplied to said second cooling apparatus.
 5. The cooler of claim 4 further comprising screen means mounted in said means for conducting material from said first cooling apparatus to said second cooling apparatus for controlling the maximum size of material supplied to the second cooling stage, and means for returning oversize material to said breaker means.
 6. The cooler of claim 5 wherein said means for conducting material from said first cooling apparatus to said second cooling apparatus includes an elevator.
 7. The cooler of claim 4 wherein said first cooling apparatus includes screen means positioned before said breaker means and by-pass means for conducting small size material around said breaker means to said means for conducting material to said second cooling apparatus.
 8. The cooler of claim 1 wherein the tubes of said second cooling apparatus are substantially rhombic in cross section.
 9. The cooler of claim 8 wherein the tubes of said second cooling apparatus are staggered in said conduit means.
 10. The cooler of claim 9 wherein the means for supplying cooling fluid to the tubes of the second cooling apparatus includes at least one fan for forcing gaseous fluid through said tubes.
 11. The cooler of claim 9 wherein the means for supplying cooling fluid to the tubes of the second cooling apparatus includes means for supplying liquid to the tubes.
 12. The cooler of claim 1 wherein there are a plurality of conduit means arranged in series in the second cooling apparatus, and conveyor means for supplying material to be cooled to each of said conduit means, the conduit means closest to said means for conducting material from said first cooling apparatus to said second cooling apparatus adapted to be filled with material before the other conduit means receive any material. 